hydrodynamic

Hydrodynamics is the branch of fluid dynamics that studies the motion of liquids and the forces acting on or by them. It encompasses the analysis of how fluids flow around bodies, how waves propagate on the surface of a liquid, and how currents develop in oceans, rivers, and pipes. In many contexts the term is used to describe the behavior of water in engineering systems, natural waters, or laboratory experiments.

The motion of Newtonian, incompressible fluids in hydrodynamics is described by the Navier-Stokes equations, together with the continuity equation. For inviscid flow, the Euler equations apply. The behavior of flows depends on the Reynolds number, which compares inertial to viscous forces and helps determine whether the flow is laminar or turbulent. Potential flow theory, which assumes irrotational and inviscid flow, provides simple analytic solutions for some cases but cannot capture boundary layers and viscous dissipation.

Analysis in hydrodynamics employs analytical methods, numerical simulations (computational fluid dynamics), and experiments in water channels and towing tanks. Dimensional analysis and similarity principles enable model testing to predict full-scale performance, aiding design and interpretation.

Applications include naval architecture (hull design, hull–propeller interaction, seakeeping), propulsion systems, offshore engineering (breakwaters, risers, platforms), and coastal and ocean engineering (wave loading, sediment transport). Hydrodynamics also informs studies of renewable energy devices such as tidal turbines and wave energy converters, as well as environmental flows and biomedical contexts where liquid motion is relevant.